Protective loading of stents

[0001] Not Applicable

[0002] Not Applicable

[0003] 1. Field of the Invention

[0004] The present invention relates generally to stents, stent loading stent contracting and stent delivery systems and their respective methods of use. Some embodiments of the invention are more specifically directed to a removable protective sheath which protects the stent from direct contact with a stent loading and/or stent contracting system. Some embodiments are more specifically directed to stent loading, contracting and/or delivery systems which are configured to accommodate such a protective sleeve and stent.

[0005] 2. Description of Related Art

[0006] A stent is a generally tubular device that is used to support a bodily lumen. A stent is typically delivered to a desired bodily location via a catheter. Often the stent is loaded onto a portion of the catheter, such as a balloon or other region of the catheter shaft. In some stent delivery systems the stent is crimped to the catheter in order to minimize the profile of the stent on the catheter and to prevent undesired movement of the stent relative to the catheter shaft.

[0007] A number of techniques for loading and contracting a stent to a catheter shaft or balloon are used. One such technique that is commonly used in the radiological suite involves hand crimping the stent to the balloon. A stent is placed over an uninflated balloon and then squeezed with the fingers until the stent is in intimate contact with the uninflated balloon. The technique is highly operator dependent and can affect stent profile and stent placement with respect to the balloon and radiopaque markers. It can also affect the dilatation length of the stent and lead to pinching of the balloon.

[0008] Other techniques for crimping stents involve the use of mechanical devices for crimping stents. Mechanical stent crimpers have been disclosed in a number of patents including U.S. Pat. Nos. 6,387,118; 6,108,886; 6,092,273; 6,082,990; 6,074,381; 6,063,102 and 5,992,000. Mechanical stent crimpers have also been disclosed in a number of copending, commonly assigned patent applications including U.S. application Ser. No. 09/401,467 now U.S. Pat. No. 6,352,547, Ser. No. 09/401,213 now U.S. Pat. No. 6,387,117, Ser. No. 09/404,986 now U.S. Pat. No. 6,769,161, and Ser. No. 09/401,218 now U.S. Pat. No. 6,360,577.

[0009] When assembling a catheter for delivery of a stent and for insertion into a body vessel, the stent is loaded onto the catheter. During the loading process the catheter and in some cases the stent is manipulated, often by hand. The manipulation of the catheter may cause the stent to be contacted and potentially damaged. Where the stent includes or is coated with a drug or other material, such contact may disturb the coating and impair the proper delivery thereof. In addition, contacting the stent during the loading and/or crimping process may result in the drug coating of the stent being contaminated with the residue of previous stent coatings that have been previously contacted by the loading and/or crimping system.

[0010] Thus, there remains a need to provide a device or mechanism for preventing direct contact between a stent, particularly a drug coated stent, and the tool or system used to load and/or crimp the stent onto the catheter shaft or balloon.

[0011] All US patents, applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.

[0012] Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.

[0013] A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.

[0014] The present invention is embodied in a variety of forms. In at least one embodiment the invention is directed to a crimpable and removable sheath or protector which may be placed onto the stent prior to the loading of the sent on to the catheter and/or crimping of the stent thereon. The protector eliminates direct contact between the loading and/or crimping apparatus and the stent. The stent used with the protector may be any type of implantable medical device. The stent may be a self-expanding, balloon expandable or hybrid stent.

[0015] In some embodiments the protector is configured to act as a disposable stent storage capsule. In some embodiments the storage capsule includes a cap assembly with a removable seal. In at least one embodiment the cap assembly is constructed and arranged to cooperatively engage a portion of a catheter assembly in order to accommodate loading of the stent thereon when the cap is unsealed.

[0016] In some embodiments the invention is directed to a contracting or crimping mould having one or more contracting apertures or openings which receive and/or draw the slack or folds of the protector which form as the stent is contracted and reduced in diameter. In some embodiments the contracting mould comprises one or more rods, each of which engage a fold of the protector to draw the folds away from the stent during contracting thereby ensuring that the points of contact between the protector and the stent remain free of folding or crinkling.

[0017] In at least one embodiment the invention is directed to a stent loading device which is constructed and arranged to be disposed about a stent delivery catheter and engage a free end of the protector. The loading device is configured to move in a linear manner relative to the catheter thereby loading the stent into the catheter while simultaneously removing the protector from about the stent.

[0018] In some embodiments a contracting mould, loading device and protector are used in conjunction with each other to reduce and load a stent onto a delivery catheter.

[0019] In at least one embodiment the stent is cooled prior to being loaded onto the catheter.

[0020] In at least one embodiment the protector comprises a heat shrink material. In some embodiments the heat shrink protector is heated as the stent is cooled, or subsequently thereto. In some embodiments the contracting mould comprises a cooling mechanism for cooling the stent and a heating mechanism for heating the heat shrinkable protector during the contraction of the stent.

[0021] These and other embodiments which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objectives obtained by its use, reference should be made to the drawings which form a further part hereof and the accompanying descriptive matter, in which there is illustrated and described embodiments of the invention.

[0035] As may be seen in FIG. 1, in some embodiments the present invention is directed to a stent protector or sleeve 10 into which a stent 12 is positioned or placed. The protector is sized to readily accommodate passage of the stent 12 therein. The protector 10 has an inner diameter 14 that is greater than the outer diameter 16 of the stent 12 positioned therein, as a result the protector 10 is provided with a sufficient amount of diameter clearance to allow the stent to pass freely inside the protector 10.

[0036] The protector 10 comprises a substantially tubular wall 20 that defines a thickness of about 0.001 inches or thinner and may in some embodiments be in the range of 0.00025 inches or less.

[0037] The protector 10 may be constructed of a variety of material selected on the basis of bio-compatibility, tensile strength, impervious structure, and resistance to low temperature cracking if it becomes subject to crumpling or tight folding. Some examples of suitable material or materials from which the protector 10 may be constructed include, but are not limited to: polyethylene terephthalate (PET), polythene and polyethylenes (PE), etc. In some embodiments the protector 10 is at least partially constructed of a heat shrink material.

[0038] As is shown in FIG. 1, the protector sleeve 10 is longer than the stent 12 and is configured to be positioned relative to the stent 12 so that at least one end of the protector 10 defines an extension 18 which extends beyond at least one end of the stent 12.

[0039] As is shown in FIG. 2, the extension 18 of the protector 10 is constructed and arranged to engage a protector retaining region 32 of a stent loading tool 30, which is distributed about a stent retaining sheath 52 of a catheter 50.

[0040] In the embodiment shown in FIG. 2 the stent 12 and a portion of the protector 10 are positioned within the contracting chamber or iris 42 of a stent contracting assembly or mould 40 for reducing the diameter of the stent 12. The mould 40 may be any type of contracting or crimping device suitable for use in reducing the diameter of a stent or other substantially tubular member.

[0041] The extension 18 of the protector 10 is positioned or drawn externally from the iris 42 and is engaged to the protector retaining region 32 of the stent loading tool 30.

[0042] As is best shown in FIG. 3, as the extension 18 extends from the mould 40 to the protector retaining region 32 of the loading tool 30, the extension 18, and eventually the entire protector 10, is drawn over a tip portion 34 of the loading tool 30. The tip portion 34 allows the stent 12 to pass into the lumen 54 defined by the stent retaining sheath 52 while drawing the protector 10 over and away from the stent and catheter 50. In this manner the stent 12 may be placed directly onto a catheter even if the catheter is not equipped with a retaining sheath.

[0043] In some embodiments such as are shown in FIGS. 2 and 3 the protector 10 passes through a profile reducing opening 27 of a stripping head or die 29 before being engaged to the protector retaining region 32 of the stent loading tool 30. Stripping die 29 ensures that the stent 12 is smoothly contracted to a size smaller than the inside diameter of the catheter sheath 52 and to give precise control of the protector 10 as it is stripped off of the stent 12. Though the stripping die 29 provides improved control and removal of the protector 10 from the stent 12, as the stent 12 is advanced into the catheter 50, the use of the stripping die 29 is not required to remove the protector 10 from the stent 12 or to insert the stent 12 into the catheter 50.

[0044] As is shown in FIG. 2 the loading tool 30 is moveably or slidingly engaged to a linear slide 36 which provides the tool 30 with the capability of being moved in a liner or longitudinal direction relative to the catheter 50. As the tool 30 slides longitudinally relative to the stationary catheter 50 about which the tool 30 is disposed, the tool 30 as well as the protector 10 and stent 12, engaged thereto via extension 18, are advanced along. As a result, as the stent 12 is guided into the lumen 54 of the retaining sheath 52 and the protector 10 is removed from about the stent 12 in the manner depicted in FIG. 3.

[0045] The particular manner in which extension 18 of the protector 10 is engaged to the protector retaining region 32 of the stent loading tool 30 may be varied. However, in the embodiment shown in FIG. 4, the protector retaining region 32 comprises a mechanical engagement comprising a retaining surface 37 about which the extension 18 is disposed and a retaining ring 38 is fitted thereon. The extension 18 is retained to the loading tool 30 by the interface of the surface 37, ring 38 and extension 18 held therebetween. Alternatively, the extension 18 may be adhesively engaged to the retaining region 32, or be otherwise chemically, mechanically or physically engaged thereto.

[0046] In the various embodiments of the invention the stent 12 may be any type of stent, graft, stent-graft, filter or other implantable medical device. In at least one embodiment the stent 12 is a “drug delivery” stent having one or more coatings or delivery mechanisms which provide the stent with the ability to transport a therapeutic agent or other substance to a legion site within the body of a patient. Because many stents employ an external coating or coatings of one or more therapeutic or other agents, the protector 10 disposed about the stent 12 will often come in contact and may even retain some residual portion of one or more coatings on its inside surface. As a result, in at least one embodiment the protector 10 is disposable and a new protector 10 is used for each stent loading procedure.

[0047] As is clear form the embodiment shown in FIG. 3, when the protector 10 is drawn over the tip portion 34 of the loading tool 30 some of the residual stent coating may be deposited on the tip portion 34 of the tool 30.

[0048] In order to reduce the potential of cross contamination of multiple stents being loaded on to a number of catheters, in some embodiments the tip portion 34 of the loading tool 30 is disposable. Alternatively, a used tip 34 may be cleaned and sterilized and then refitted on the loading tool 30 as desired. In at least one embodiment the tip 34 is at least partially constructed from a low surface friction material such as stainless steel, PTFE, etc. In some embodiments the tip comprises a cone angle of about 10 to about 60 degrees. Preferably, the cone angle of the tip 34 is about 20 degrees to about 45 degrees.

[0049] As indicated above, in some embodiments of the invention the protector 10 may be utilized as a disposable and sealable stent storage capsule, such as is indicated generally at 60 in FIG. 5. A capsule 60 comprises a protector sleeve 10 which is sealed at one end 62 and comprises a seal assembly 66 at the opposing open end 64. Assembly 66 includes a seal housing 68 engaged to the open end 64 of the protector 10. The seal housing 68 may be considered to define at least a portion of the protector extension 18. An end cap 70 is removably engaged to the seal housing 68. In at least one embodiment of the invention the end cap 70 is pivotally engaged to the housing 68, at a pivot 71 as is illustrated in FIG. 6. When the cap 70 is removed from the seal housing 68 the stent 12 may be accessed in the manner previously described.

[0050] As is shown in FIG. 6 the seal assembly 66 provides the capsule 60 with a ready mechanism for engaging the seal housing 68 of the extension 18 directly to the protector retaining region 32 of the stent loading tool 30. A ring 38 or any other desired mechanism may be utilized to engage the housing 68 of the open capsule 60 to the loading tool 30.

[0051] When the stent 12 and protector 10 are positioned within the contracting mould 40, the stent will often be supported by a mandrel 80. Mandrel 80 may be incorporated into or positioned adjacent to an iris chilling system 82, which acts to chill the iris 42 and thus the stent 12 prior to contraction within the mould 40.

[0052] In addition to the above, a significant advantage that the protector 10, as described herein provides, is that when the stent 12 is contracted via mould 40, such as is shown in FIG. 7, and the diameter of the stent 12 is reduced, the protector 10 is readily deformable so that any excess of slack exhibited by the protector 10 may be formed into one or more folds 41 which may be pulled, or otherwise drawn away from the stent 12 into one or more spaces 44 between the individual contracting members or blades 46 of the iris 42.

[0053] In some embodiments, an example of which is shown in FIG. 8 the mould 40 is provided with an internal air pressure which applies a predetermined force or pressure, indicated by arrows 43, against the inner diameter 14 of the protector wall 20. As a result, the protector 10 is held against the blades 46 through out the contracting process. As the stent 12 is contracted, the folds 41 of the protector 10, which form as a result of the diameter of the stent 12 diminishing, are pushed or drawn into the spaces 44 between the blades 46 as a result of the force 43 applied by the internal pressure within the protector 10. In some embodiments a negative pressure, such as provided by a vacuum may be provided to the spaces 44 between the blades 46 in order to draw or pull the folds 41 into the spaces 44.

[0054] It should be noted that in at least one embodiment, prior to subjecting the stent 12 and protector 10 to the advancement described herein, the stent is cooled or chilled to a desired temperature and fully contracted by the mould 40. Following this cooling and contracting process, the stent 12 and protector 10 are advanced in the manner described.

[0055] In at least one embodiment of the invention the protector 10 has some heat shrink properties or comprises a heat shrink material. A stent 12 and heat shrink protector 10, such as is shown in FIG. 9 may be inserted into the mould 40. The mould 40 may comprise a heating mechanism 90, that injects heated air or other medium, indicated by arrows 91 onto the protector 10. The heat provided by the heated medium 91 provides the protector 10 with sufficient energy to activate the heat shrink properties of the protector 10. As the protector 10 contracts as a result of its heat shrink properties, the folds 41 of the protector 10 are drawn into the spaces 44 between the blades 46, such as shown in FIGS. 7 and 8, or roller members or rods 47 such as are shown in FIGS. 11 and 12.

[0056] By providing the protector with heat shrink properties the amount of excess material forming folds as the stent is contracted may be reduced or even eliminated. In embodiments where excess material of the reduced diameter protector is sufficiently minimized so that folds are not formed, or the folds are so insubstantial that they are unable to be drawn between the blades or roller members of the mould it may be necessary to cut and unwrap the protector from the stent following the contracting process.

[0057] As is shown in FIG. 9, in some embodiments the mould 40 may be provided with a cooling pipe 92 about which the stent 12 and protector 10 are disposed within the mould 40. The cooling pipe may act as a mandrel 80 as previously described. The cooling pipe 92 may be provided with a reduced temperature relative to the stent 12 to conductively cool the stent 12 to a desired temperature, prior to, during, or subsequent to the contracting process.

[0058] In at least one embodiment, an example of which is shown in FIG. 10, the cooling pipe 92 defines a plurality of openings or perforations 93 through which a coolant, indicated by arrows 94, such as for example atomized liquid cryogenic fluid, may be injected to directly cool the stent 12 to a desired temperature. The coolant 94 is supplied by the chilling system 82 with which the cooling pipe 92 may be in fluid communication.

[0059] Because the cooling pipe 92 is positioned within the stent 12, and it is necessary to remove the stent 12 and protector 10 from the mould 40, the diameter of the cooling pipe 92 must be less than or equal to the inside diameter of the stent 12 after the stent 12 has been contracted by the mould 40.

[0060] In some moulds, an example of which is shown in FIG. 11, the mould 40 defines a substantially cone shaped iris 42 of gradually decreasing diameter into which the stent 12 is inserted in order to contract and reduce the diameter of the stent according to the smallest diameter of the iris 42. Iris 42 defines a plurality of spaces 44 each of which extend from the iris opening 45 to a rotatable roller member 47. As shown in FIG. 12, each opening and rod member 47 is constructed and arranged to engage a fold of the protector 10 and as the stent and protector are advanced through the mould 40 the rods 47 rotate to draw the increasing slack of the folds away from the stent 12.

[0061] The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

[0062] Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.

[0063] This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.